Abstract
In this study, we evaluated a two-step process for detoxification of waste roofing slate, involving cement hydrate removal and low temperature detoxification using oxalic acid. These treatments were conducted on raw material and intermediate product, respectively. Cement hydrate removal effectively eliminated most Ca-containing cement hydrate components from the raw material under the following conditions: HCl to solid ratio: 0.456 g/g, reaction time: 2 h, and solid to liquid ratio: 0.124 g/mL. Following low temperature (~100 °C) detoxification of intermediate product obtained after cement hydrate removal, chrysotile in waste roofing slate was effectively transformed to Mg-oxalate under conditions of oxalic acid to solid ratio of >0.67 g/g.
Highlights
Asbestos-containing materials (ACMs) have been widely used since 4000 B.C. for various applications, due to their high mechanical strength and low heat conductivity [1]
The XRD chart clearly shows that chrysotile peaks in the raw material disappeared after the low temperature detoxification process, and Mg-oxalate could be identified as the main component under all oxalic acid to solid ratio, temperature, and reaction time conditions
The low temperature detoxification test using chrysotile clearly showed the effectiveness of the proposed process
Summary
Asbestos-containing materials (ACMs) have been widely used since 4000 B.C. for various applications, due to their high mechanical strength and low heat conductivity [1]. Asbestos includes two groups of commonly occurring silicate minerals: the serpentine group (e.g., chrysotile) and the amphibole group (e.g., actinolite, amosite, anthophyllite, crocidolite, and tremolite). Of these minerals, chrysotile is the most widely used (90% of world production) [2]. Chrysotile is the most widely used (90% of world production) [2] It consists of alternating silicate tetrahedral sheets and brucite (Mg(OH)2 ) octahedral sheets and has a cylindrical structure due to structural discordances in mineral lattices, resulting from the substitution of Si4+ to Al3+ and Mg2+ to. Due to its severe carcinogenicity, the use of asbestos is nowadays strongly prohibited in many developed countries. South Korea has likewise prohibited the use, transport, modification, and unauthorized reclamation of asbestos and asbestos-containing materials since 2003
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